Earth-class planet

An Earth-class planet is a planet having a mass 0.5 to 10 times that of the Earth (Me)
and a radius 0.8 to 2.2 times that of the Earth. Planets more massive than
10 Me have enough gravity to attract a large hydrogen-helium
atmosphere and so become gas giants. Those
less massive than 0.5 Me are likely to lose any potentially
life-supporting atmosphere because of low gravity and lack of plate
tectonics needed to recycle carbon dioxide back into the atmosphere.